Endoscopes are widely used in many medical procedures for viewing otherwise inaccessible areas of bodily organs, cavities, passageways, etc. Generally, endoscopes include an elongate catheter body, or similar structure wherein optical fibers are arranged both for transmitting illumination to the distal end of the catheter body to illuminate a viewing field, and for carrying the optical image back to the physician. One or more lenses may be positioned on the distal end of the endoscope to focus the optical image received by, or the illumination cast by the instrument.
In many applications it is desirable that the catheter portion of the endoscope be "steerable", bendable or maneuverable from the proximal end of the scope to facilitate guidance of the catheter portion through tortuous or furcated anatomical passageways. Additionally, the ability to bend the catheter portion of the scope at or near its distal end may enable the operator to visually scan an expanded viewing area by bending or otherwise manipulating the distal end of the scope. Indeed, in many applications it is desirable that the distal end of the scope be capable of undergoing a full 180.degree. or more of deflection so that the operator may "look back" at a site behind or proximal to the distal end of the scope. Such "retro-viewing" is often desirable, for example, when examining the puncture site of a gallbladder during a procedure. Second, the ability to maneuver the tip makes it easier to guide the tip of the endoscope properly through the often highly branched and convoluted passageways near organs such as the coronary arteries of the heart or the branched ducts of the biliary tree.
There are accordingly a large number of endoscopes now available. The following patents show examples of existing devices and methods for manufacturing maneuverable catheters, endoscopes, and the like:
______________________________________ No. Inventor(s) Issue Date ______________________________________ 4,934,340 Ebling et al. June 19, 1990 4,911,148 Sosnowski et al. March 27, 1990 4,899,732 Cohen February 13, 1990 4,669,172 Petruzzi June 2, 1987 4,418,688 Loeb December 6, 1983 3,998,216 Hosono December 21, 1976 3,946,727 Okada et al. March 30, 1976 3,739,770 Mori June 19, 1973 3,572,325 S. Bazell et al. March 23, 1971 3,610,231 Nagashige Takahashi October 5, 1971 3,521,620 W. A. Cook July 28, 1970 ______________________________________
Similar devices are disclosed in the following non-U.S. texts:
U.K. Patent Application No. GB 2 130 885 A (F. A. Coulston-Iles, published Jun. 13, 1984);
U. K. Patent Specification No. 1 208 639 (Cook, published Oct. 14, 1970);
European Patent Application No. 253 687 (Millar et al., published Jan. 20, 1988); and
European Patent No. EP 370 785, (issued to Medical Institute, Inc., May 30, 1990).
In order to control the deflection of the distal tip of an endoscope, many designs incorporate one or more activation wires that run the length of the endoscope. These are attached to the distal tip, which often is in the form of a stack of hollow rings which are attached to each other and allow pivoting of each ring relative to its neighbor. By pulling on an activation wire, the distal end deflects towards the wire.
The designer of wire-activated endoscopes is faced with several conflicting requirements. The diameter of the endoscope should be as small as possible so that the endoscope can be maneuvered into the smallest possible passageways and cavities. On the other hand, the outer casing of the endoscope should be as strong as possible to avoid breaking, kinking, and buckling. It should also be stiff to promote the accurate and predictable transmission of torque. At the same time, the activation wire must be able to withstand the tensile load required to deflect the distal end of the endoscope. If, however, the endoscope has either thick outer walls or a mainly solid cross-section, its bending moment will increase and require the activation wire to bear and transmit even greater force in order to deflect the tip. Also, a stiff endoscope will not easily traverse tortuous tracts. Additionally, small-diameter endoscopes have a small moment arm for the activation wire, so that the activation wire must transmit greater force to achieve a given moment.
In order to decrease the diameter of the endoscope, activation wires, if such are even provided, are typically unprotected and are usually welded or soldered directly to the outer casing of the instrument. This arrangement, however, decreases the tensile strength of the wires and reduces the bending force they can bear and transmit to the tip. It also increases the risk of buckling not only of the outer casing, but also of the activation mechanism itself. An additional disadvantage of thick-walled designs, or designs having mostly solid cross-section, is that the area left over for carrying illumination and optical fibers, working lumens, etc., is correspondingly decreased.
Additional typical disadvantages of many existing endoscope designs are that they bend only in one direction (which means that the entire scope must be rotated in order to see in the other direction), and that they are often difficult to manufacture. Furthermore, existing designs that incorporate activation wires typically join these wires to the outer casing of the scope using methods such as soldering or welding that either weaken the wires themselves or decrease the force they are able to bear and transmit.
One object of this invention is therefore to provide an endoscope or "miniscope" that is simple to build, rugged and compact, that avoids the problem of buckling, that has a small outer diameter, and that provides full tip deflection using activation wires that are mounted and joined in such a way that they are able to transfer relatively large activation forces securely.